The present invention mainly relates to a method for assembling sheet metals, preferably metallic sheets obtained by rolling, and to a rigid structure obtained by said method, such as an industrial cooking utensil.
It is normal to place hams to be cooked, wrapped or not in plastic bags, in stackable cooking utensils, comprising a plurality of parallel channels ensuring the holding of these hams during the cooking, to stack the utensils and to dispose the stack of utensils with hams to be cooked in a cooking unit into which a heat transfer fluid is made to enter. The channels, possibly associated with covers, confer the required shape on the hams.
These cooking utensils incorporate stainless steel sheets formed mechanically and assembled by welding. These sheets have to be positioned and kept in the required configuration during the operations of connecting them by welding. Thus these operations (positioning, holding and welding) are carried out manually, which increases the cost price of such a cooking utensil. In addition, any lack of precision in the positioning causes a variation in the geometry of the utensils, which become more difficult to stack.
Consequently one aim of the present invention is to obtain a method for producing a rigid structure produced mainly from sheet metals, notably a method for producing an industrial food cooking utensil or a component of such a cooking utensil, providing the immobilisation of the sheets to be assembled by welding and/or brazing before and during this welding and/or brazing step in a relative position corresponding to the relative positions of the said sheets after final connection by welding and/or brazing.
Another aim of the present invention is to offer such a method easy to implement and able to be executed by unskilled personnel.
Another aim of the present invention is to offer such an automatable and/or automated method. Notably, the forming such as cropping and folding is advantageously carried out automatically. Likewise, another aim of the present invention is to offer such a method providing automatic welding by a welding robot.
Another aim of the present invention is to offer a rigid structure of high precision, notably an industrial cooking utensil.
Another aim of the present invention is to offer identical assemblies with a rigid structure adapted to each other, notably stackable with very small dimensional variations from one structure to another, so as to facilitate the assembly thereof, notably the stacking.
These aims are achieved by a method according to the present invention including a step consisting in providing, in at least one sheet metal, a recess such as a notch, a cavity or, advantageously, an opening for receiving a projecting element on a second sheet metal with which the first sheet must be connected. Advantageously, the openings and the projecting elements are produced by cutting with a beam such as for example a plasma beam, or advantageously a laser beam, typically infrared, for example produced by a CO2 laser. Advantageously, the cutting beam is guided automatically by a numeric-control automatic cutting apparatus.
Advantageously, the periphery of the sheet metal is also cut with the same beam, substantially simultaneously, that is to say during the same cutting operations as the cutting of the openings for receiving projecting elements. For elongate sheets, notably substantially rectangular ones having large sides and two small sides, the projecting elements are advantageously situated on the small sides. Advantageously, the sheet metal provided with projecting elements has a constant or substantially constant thickness, over its entire surface, including at the level of the projecting elements.
Advantageously, the projecting element or elements are disposed in line with the part of the sheet metal which carries them. Notably, for a flat sheet, the main faces of the projecting element are situated in two parallel planes defined by the main faces of the sheet.
The same sheet can include a projecting element for matching a second sheet and an opening for receiving a projecting element on a third sheet.
The welding can be carried out on all or some of the contact areas between the sheets and notably, but not necessarily, at the level of the projecting elements.
The assembly according to the present invention is particularly effective for perpendicular sheets.
The assembly according to the present invention, by the introduction of projecting elements into cavities or advantageously into openings, can also use walls provided with complementary notches also providing the assembly of various sheets. The nested elements can also be connected by welding and/or brazing.
An industrial cooking utensil according to the invention advantageously has parallel channels for receiving food, notably hams, and a rectangular peripheral frame typically composed of four sheets. The ends of the channels are provided with projecting elements whilst the sheets of the frame receiving the ends of the channels are provided with notches, or advantageously openings for receiving the said projecting elements. The projecting elements and their associated reception openings are disposed so that the nesting can take place only in the required relative positions of the channels with respect to the peripheral frame.
The object of the present invention is principally a method for assembling a rigid structure including at least a first sheet and a second sheet, characterised in that it includes the steps consisting in
a) conferring the required shape on a first sheet and providing a recess for receiving a projecting element on a second sheet at the required contact location between the said recesses in the first sheet and a projecting element on the said second sheet;
b) conferring the required shape on a second sheet and providing a projecting element whose geometry is adapted to enter the recess in the first sheet, at the required contact location between the projecting element in the second sheet and the recess in the first sheet;
c) providing the temporary connection of the first sheet to the second sheet by nesting the projecting element on the second sheet in the recess in the first sheet;
d) providing the final connection of the first sheet and of the second sheet by welding or brazing in the same relative positions as those of the sheets achieved at step c).
Another object of the present invention is a method for assembling a rigid structure, characterised in that the two sheets are assembled at right angles.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the recess is an opening passing through the first sheet from one side to the other.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the length of the projecting element is less than the thickness of the first sheet.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the second sheet is provided with a projecting element at a first end and with a second projecting element at a second end, each of the projecting elements being nested in a recess in two different first sheets.
Another object of the present invention is a method for assembling a rigid structure, characterised in that steps a) and b) are performed by cutting on a numeric-control cutting apparatus.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the numeric-control cutting apparatus has a power laser.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the second sheet has a plurality of projecting elements, in that step b) includes a sheet folding operation and in that, at step a), the recesses are produced in the first sheet corresponding to the position of these projecting elements on the second sheet after folding of this second sheet.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the first sheet or its second sheet includes a notch for receiving a transverse sheet having a complementary notch.
Another object of the present invention is a method for assembling a rigid structure, the said structure having a rectangular peripheral frame, characterised in that it includes a step of connecting the sheets of the rectangular peripheral frame with internal sheets followed by a subsequent step of welding or brazing the ends of the sheets of the said frame.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the welding or brazing for assembling the sheets is a welding by transparency effected from the face of the first sheet opposite to the one receiving the end of the first sheet.
Another object of the present invention is a method for assembling a rigid structure, characterised in that the welding or brazing carried out over the entire contact surface between the end of the second sheet and the first sheet.
Another object of the present invention is a structure produced by the method, characterised in that it includes at least two sheets assembled by welding or brazing, a first sheet having a recess containing a projecting element on the second sheet.
Another object of the present invention is a structure characterised in that the projecting element is a rectangular parallelepiped.
Another object of the present invention is a structure characterised in that the projecting element is disposed in line with the second sheet.
Another object of the present invention is a structure characterised in that the said structure is an industrial cooking utensil.
Another object of the present invention is a structure characterised in that the said structure is an industrial ham cooking utensil having a plurality of parallel channels, each channel being provided at each of its ends with at least one projecting element for connection with an end sheet.